By CASEY MCNERTHNEY, SEATTLEPI.COM STAFF

Published 10:00 pm, Wednesday, April 21, 2010

Police found Glennis Parker in a 76 gas station parking lot, sitting in the driver's seat of his GMC truck. He'd been shot three times in the head.

Investigators have said little about the Feb. 9 killing -- the third of four homicides in Seattle this year. But court documents released Thursday show that in the days after the homicide, police wanted to talk to Parker's stepson, who had argued with Parker about an hour before he was found dead.

Police are investigating a tip that that the stepson shot Parker because he thought Parker had been molesting the suspect's mentally disabled brother. The allegation hasn't been proven.

The morning of Feb. 9, the adult stepson and Parker exchanged words at the Central District home where Parker and the stepson's mother lived, police were told. At 1:36 a.m. someone at the home called police.

At least two men could be heard in what police describe as a loud and aggressive verbal disturbance. Parker's wife -- the suspect's mother -- can also be heard in the background. The call ends without the caller addressing the 911 operator.

The 911 dispatcher called back and the woman answered the phone. She said there was no problem other than a loud discussion, according to police.

Investigators believe the only people at the home were Parker, his wife, the adult stepson he argued with and the disabled stepson.

Police were told the suspect left the house before Parker, who later left by himself in the early morning. His wife became concerned when Parker didn't answer the phone and went looking for him.

She drove to the shooting scene at Terry Avenue and James Street, but claimed to police she didn't speak to anyone about what occurred or what happened at the shooting scene.

The woman arrived shortly after 4 a.m., about 90 minutes after Parker was found dead, and was very distraught. Police say she told about a "loud discussion" her husband had with someone at their home earlier that morning. She initially wouldn't identity the other person, but later conceded it was her stepson, according to court documents.

Parker's widow told police her son left right after the initial 911 call and that she hadn't spoken to him. She also claimed not to have any contact numbers for him, according to court documents.

For several days after the shooting, detectives attempted to locate and interview that stepson. His family continued to deny any contact with him, though police say that may not be the case.

On Feb. 11, detectives received a declaration signed by the suspect from a defense attorney in which he declined to speak with detectives.

That same day, police received the anonymous tip that that the stepson, who has not been charged, shot Parker because he thought he'd been molesting the suspect's mentally disabled brother.

The investigation showed that the night of the homicide, a man resembling the stepson upset at someone for hurting his brother. The man resembling the stepson was less than a mile from the shooting scene, according to court documents.